Study on degradation of Basic Violet 1 and heat generation by parallel orifice plate hydrodynamic cavitation

Hydrodynamic cavitation (HC) technology with double parallel orifice plates can further enhance the degradation effect and heat generation efficiency and play an important role in practical large-scale organic wastewater treatment and energy saving. In this study, based on the optimal hole numbers in single orifice plate, the influences of the hole number and distribution in double parallel orifice plate on Basic Violet 1 (BV-1) degradation and heat generation are studied in detail. Furthermore, the effects of some experimental parameters (inlet pressure, initial concentration, solution temperature and solution volume) on BV-1 degradation and heat generation in 4 + 4 parallel orifice plate HC system are deeply studied. Then, the effect of added H 2 O 2 on the BV-1 degradation and heat generation is also investigated. In addition, the capturing experiments of free radicals (•OH and •O 2 - ) are carried out. Finally, the BV-1 degradation pathway and possible degradation mechanism are proposed by analyzing the data of UV–vis spectrum, LC-MS and total organic carbon (TOC). The final results show that the solution temperature can be raised from 20.05 °C to 57.71 °C under the experimental conditions of 4 + 4 parallel orifice plates, 3.0 bar inlet pressure , 5.0 L total solution volume and 10 mg/L initial concentration for 90 min continuous circulation and the BV-1 degradation ratio can be achieved by 75.98 %. The system can generate 785.40 kJ heat at 48.50 USD/m 3 cost and achieve 29.09 % thermal efficiency . For 1:30 molar ratio of BV-1 and H 2 O 2 , the solution temperature can be further raised to 63.32 °C in 90 min continuous cycling. 95.38 % BV-1 degradation ratio can be obtained and the 909.72 kJ heat can be generated, reaching the 33.69 % thermal efficiency. It is hoped that this work can provide a new strategy for enhancing the degradation of organic dyes and resource utilization of heat by using double parallel orifice plate HC technology.